This invention relates to apparatus for and a method of forming cellular honeycomb material, and more particularly to such apparatus and method in which segments of a composite web are bonded together in a stack to form a continuous core of compressed honeycomb material.
Honeycomb material is conventionally produced by either a rotary-type apparatus, such as disclosed in my U.S. Pat. No. 3,218,217, or by a segmenting-type apparatus, such as shown in U.S. Pat. No. 3,257,253. In my prior rotary-type apparatus, the cellular honeycomb material is formed by feeding forward a single web of paper or the like, longitudinally scoring the web, forming transverse lines of intermittent slits across the web, applying longitudinal stripes of glue to the web, and then folding the slitted web by means of a pair of meshing star wheels which pleat the web. The pleated web is then compressed between a pair of spaced guides to insure the pleats are bonded to one another along the various glue lines to form a compressed honeycomb core with the height of the pleats determining the thickness of the honeycomb core. While my prior art apparatus does continuously produce the honeycomb material at efficient production speeds, there is a tendency for the slitting rolls on a wide machine to deflect which may cause the slits in the web to be improperly cut and thus effects irregularities in the expansion of the honeycomb core produced. Also, with my prior rotary apparatus, it is an involved operation to modify the apparatus so as to produce honeycomb material of different thicknesses because it is necessary to change the slitting rolls and the star wheels for other rolls and star wheels of a different diameter. It is also necessary to change the drive ratio of the apparatus.
In the segmenting-type apparatus, shown in the above-mentioned U.S. Pat. No. 3,257,253, a composite web with glue stripes applied to one face thereof is continuously fed downwardly in a vertical reach into intermittently operable segmenting blades. A vertical web take-up is provided between the glue rolls and the segmenting blades. This web take-up allows the web to be continuously infed and intermittently outfed. Initially, excess web is infed into the take-up thereby causing the web to buckle so that upon the web being permitted to move into the segmenting means, these buckles forceably push the web downwardly into the blades. However, because the stiffness of these composite webs may vary considerably (depending on the physical properties of the webs constituting the composite web which may vary with the thickness of the webs, changes in humidity and the degree to which the webs are wetted by the glue), there is a tendency for the stored energy in the web to vary. Thus the stored up energy may be insufficient to insure that the web is fully advanced before it is segmented while in other instances excess web may be advanced past the blade before it is segmented. In either instance, honeycomb material of uneven height is produced.